Dosing unit, ambulatory infusion device comprising dosing unit and method for operating a dosing unit

ABSTRACT

A dosing unit for an ambulatory infusion device and a method of operation are disclosed. The dosing unit includes a stationary member, a movable member, and a plunger. The movable member and the stationary member, together, make a charging valve and a discharging valve. The plunger is located, at least in part, in a metering cavity of the movable member and the movable member is adapted to selectively couple and decouple a driving unit, such that, by operating the driving unit with the movable member being coupled with the driving unit, the movable member moves with the plunger to maintain a position of the plunger relative to the movable member along a displacement axis, and by operating the driving unit with the movable member being decoupled from the driving unit, the plunger is displaced while the position of the movable member is maintained.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/046,022, filed Mar. 11, 2011, which is a continuation ofInternational Application No. PCT/EP2009/005447 filed Jul. 28, 2009,which claims priority to European Application 08016075.7 filed Sep. 12,2008.

TECHNICAL FIELD

The present disclosure is related to dosing units for ambulatoryinfusion devices and to ambulatory infusion devices comprising suchdosing units.

BACKGROUND

Ambulatory infusion devices are known, for example, in the therapy ofDiabetes Mellitus by Continuous Subcutaneous Insulin Infusion (CSII), aswell as in pain therapy or cancer therapy. Those ambulatory infusionpumps are manufactured, among others, by Disetronic Medical Systems AG,Switzerland, and are available, e.g., under the name ACCU-CHEK® Spiritfor CSII therapy.

The above-referenced ambulatory infusion devices are typically a syringedriver type. A number of drawbacks of such syringe driver type devicesare known in the art. In particular, these devices have limitedprecision because they meter very small drug amounts, typically in thenano-liter range, out of a drug cartridge having an overall drug volumein the milliliter range. Therefore, additional concepts andarchitectures have been proposed that use a dedicated dosing unitdownstream from the drug reservoir. These concepts include a micromembrane pump or a micro piston pump that are coupled to a drugreservoir and designed for precise metering of small volumes. Whileseveral designs for such dosing units are known in the art, they arecomplex, expensive and difficult to manufacture at a large scale becausethey integrate a number of components, including metering components andvalves, and are frequently made from materials that are costly and/ordifficult to manufacture, such as silicon. Accordingly, improved dosingunits and ambulatory infusion devices comprising dosing units arerequired.

SUMMARY

In one embodiment, a dosing unit for an ambulatory infusion deviceincludes a stationary member, a movable member, and a plunger. Themovable member and the stationary member, in combination, make acharging valve and a discharging valve, where the charging valve isadapted to be in fluid communication with a drug reservoir and thedischarging valve is adapted to be in fluid communication with an outletassembly. The movable member is movable between a charging valveposition, in which the charging valve is open and the discharging valveis closed, and a discharging valve position, in which the dischargingvalve is open and the charging valve is closed. The plunger is located,at least in part, in a metering cavity of the movable member and isadapted to displace in the metering cavity along a displacement axisbetween a distal plunger end position and a proximal plunger endposition. The plunger is adapted to couple continuously to a drivingunit and the movable member is adapted to selectively couple anddecouple to the driving unit such that, by operating the driving unitwith the movable member being coupled with the driving unit, the movablemember moves with the plunger as to maintain a position of the plungerrelative to the movable member along the displacement axis, and that, byoperating the driving unit with the movable member being decoupled fromthe driving unit, the plunger is displaced while a position of themovable member is maintained.

In another embodiment, a method for operating a metering unit for anambulatory infusion device includes providing a dosing unit and adriving unit, coupling a plunger of the dosing unit, the plunger beinglocated, at least in part, in a metering cavity of a movable member ofthe metering unit and being adapted for displacement in the meteringcavity along a displacement axis. The method also includes coupling themovable member of the dosing unit to the driving unit with the plungerbeing further coupled to the driving unit, moving the movable memberinto a charging valve position with a position of the plunger relativeto the movable member along the displacement axis being maintained. Themethod further includes decoupling the movable member from the drivingunit with the plunger being further coupled to the driving unit,displacing the plunger along the displacement axis in a distal directionwith the position of the movable member being maintained, thus chargingthe metering cavity, coupling the movable member of the dosing unit withthe driving unit, with the plunger being further coupled to the drivingunit, and moving the movable member into a discharging valve position,with the position of the plunger relative to the movable member alongthe displacement axis being maintained. The method further includesdecoupling the movable member from the driving unit with the plungerbeing further coupled to the driving unit, and displacing the plungeralong the displacement axis in a proximal direction with the position ofthe movable member being maintained, thus discharging the meteringcavity.

The following text sets forth a broad description of numerous differentembodiments of the present invention. The description is to be construedas exemplary only and does not describe every possible embodiment sincedescribing every possible embodiment would be impractical, if notimpossible, and it will be understood that any feature, characteristic,component, composition, ingredient, product, step or methodologydescribed herein can be deleted, combined with or substituted for, inwhole or part, any other feature, characteristic, component,composition, ingredient, product, step or methodology described herein.Numerous alternative embodiments could be implemented, using eithercurrent technology or technology developed after the filing date of thispatent, which would still fall within the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent invention can be best understood when read in conjunction withthe drawings enclosed herewith and in which:

FIG. 1 depicts a schematic view of a dosing unit according to one ormore embodiments of the present disclosure;

FIG. 2 depicts a schematic view of a dosing unit according to one ormore embodiments of the present disclosure;

FIG. 3 a depicts a schematic view of a movable member and a plunger of adosing unit according to one or more embodiments of the presentdisclosure;

FIG. 3 b depicts a schematic view of a movable member and a plunger of adosing unit according to one or more embodiment; and

FIG. 4 depicts a schematic view of an ambulatory infusion deviceaccording to one or more embodiments of the present disclosure.

The embodiments set forth in the drawings are illustrative in nature andnot intended to be limited of the invention defined by the claims.Moreover, individual features of the drawings and invention will be morefully apparent and understood in view of the detailed description.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to dosing units andambulatory infusion devices comprising dosing units that are reliableand cost efficient in large scale manufacture, as well as methods foroperating such dosing units. Some aspects of such dosing unit aredisclosed by co-owned European patent application No. 07104240.2.

In one embodiment, the present disclosure is direct towards a dosingunit for an ambulatory infusion device, where the dosing unit includes:

a) a stationary member; and

b) a movable member, where

the movable member and the stationary member, in combination, make acharging valve and a discharging valve. The charging valve is adapted tobe in fluid communication with a drug reservoir and the dischargingvalve is adapted to be in fluid communication with an outlet assembly.The movable member is movable between a charging valve position, inwhich the charging valve is open and the discharging valve is closed,and a discharging valve position, in which the discharging valve is openand the charging valve is closed. The dosing unit also includes:

c) a plunger located, at least in part, in a metering cavity of themovable member and adapted for displacement in the metering cavity alonga displacement axis between a distal plunger end position and a proximalplunger end position, where the plunger is adapted to couplecontinuously to a driving unit and the movable member is adapted toselectively couple and decouple to the driving unit. By operating thedriving unit with the movable member being coupled to the driving unit,the movable member moves with the plunger as to maintain a position ofthe plunger relative to the movable member along the displacement axis,and that, by operating the driving unit with the movable member beingdecoupled from the driving unit, the plunger is displaced while aposition of the movable member is maintained.

The stationary member and the movable member may include a set of valveapertures such that a movable charging valve aperture is aligned with astationary charging valve aperture if the charging valve is open and amovable discharging valve aperture is aligned with a stationarydischarging valve aperture if the discharging valve is open. In someembodiments, the movable member includes a single movable valveaperture, which may serve as both the movable charging valve apertureand the movable discharging valve aperture depending on the position ofthe movable member.

In some embodiments, neither the charging valve nor the dischargingvalve is open if the movable member is in a position other than thecharging valve position or the discharging valve position.

In some embodiments, the movable member and the stationary membercontact each other around the valve apertures to form a fluid-tightseal. The sealing force resulting from this contact may be used tocontrol operation of the metering unit in some embodiments, as will bedescribed below. In some embodiments, the stationary member also servesas a bearing for the movable member.

The metering cavity includes a closed proximal front and an open distalfront. The metering cavity may be limited by a front face, which isformed by the inner face of a proximal front wall of the movable member,and a circumferential face, which is formed by the inner face of acircumferential wall of the movable member. The at least one movablevalve aperture may be located in close axial proximity to the proximalfront or in the proximal front of the metering cavity. In the proximalplunger end position, a proximal plunger front may be close to theproximal front and/or contact the proximal front of the metering cavity.As used herein, the terms “proximal” and “distal” are discussed inreference to the proximal front. Accordingly, the proximal direction isthe direction pointing away from the distal front along the displacementaxis towards the proximal front, while the distal direction is thedirection pointing away from the proximal front along the displacementaxis towards the distal front. As used herein, the proximal plungerfront is used as reference for the plunger position along thedisplacement axis. Alternatively, however, the charging valve and thedischarging valve may be located at the distal end of the movablemember, with certain modifications being required.

The proximal plunger front forms a movable limiting surface of avariable metering volume, where the other limiting surfaces of themetering volume are defined by the surfaces of the metering cavity. Themetering volume is the fluid filled volume of the metering cavity. Ifthe plunger is in the proximal plunger end position, the metering volumeis minimal and/or approaches zero. If the plunger is in the distalplunger end position, the metering volume is maximal.

The section of the metering cavity in which the proximal plunger frontmay move, i.e., the section axially defined by the distal plunger endposition and the proximal plunger end position, is referred to as themetering section. The axial distance between the distal plunger endposition and the proximal plunger end position is referred to as thedisplacement distance.

The plunger may include a plug section, which is in fluid contact withits proximal front, where the proximal front of the plug section is theproximal plunger front. The circumference of the plug section and theinner face of the metering section, in combination, form a fluid tightseal. Alternatively to a plug section being part of the plunger, a plugmay be coupled to the plunger. For clarity reasons, however, theproximal front of the plug is also referred to as the “proximal plungerfront” if the plug is a dedicated element.

In some embodiments, the metering cavity is cylindrical, where thecylinder axis of the metering cavity is the displacement axis. Theplunger and the movable member, in combination, form a syringe-likecomponent. The outer shape of the movable member may, at least in part,be cylindrical, such that the movable member is a hollow cylinder closedat its proximal front by a proximal front wall and open at its distalfront, and include a cylindrical circumferential wall.

For the usage in the framework of diabetes therapy by CSII, the dosingunit may be designed for a maximum metering volume in the range of 4 to20 International Units. For some embodiments that include a cylindricalmetering cavity, the ratio of the displacement distance of the plungerto the diameter of the metering cavity may be in a range of 1:1 to 10:1.However, other dimensions, as well as larger or smaller ratios arecontemplated.

The dosing unit may be a disposable product that is used foradministering the drug volume contained within one drug reservoir only.The components of the dosing unit are, at least in part, made fromplastic and manufactured by standard injection molding techniques. Theplug section of the plunger or a separate plug may be made from a rubberor plastic material and may include seal features such as O-ring sealsthat are in contact with the inner circumferential face of the meteringcavity. In some embodiments, the plug section is integral withadditional components of the plunger. In some embodiments, the plungeris made in one piece.

If the movable member is coupled to the driving unit, the movable memberis coupled to the driving unit directly or via intermediate components.In some preferred embodiments, the movable member couples to the drivingunit via the plunger, as described below in more detail.

The coupling of the movable member to the drive unit may be continuousfor the time of the metering sequence of the dosing unit. The movablemember may, however, be decoupled from the drive unit for a short time,e.g., for cleaning or checking purposes where required in someembodiments. The metering sequence time of a dosing unit is typically onthe order of a few days for the metering sequence in insulin infusiondevices. The lifetime of the drive unit may be much longer, for example4 years and/or generally unlimited.

In some embodiments, the movable member and the plunger movesynchronously, that is, without relative motion, when operating thedriving unit to which the plunger is coupled.

As used herein, the term “couple” refers to an operative couplingincluding a coupling capable of force and/or torque transmission suchthat an element coupled to the driving unit may be moved by a forceand/or torque received from the driving unit. The movable member isreferred to as being “coupled” if it is coupled to the driving unit andis referred to as being “decoupled” if the movable member is decoupledfrom the driving unit.

Embodiments of dosing units according the present disclosure allowmetering sequences to be performed in a cyclical manner, where ametering sequence is described by a charging subsequence and adischarging subsequence, where each subsequence includes a valveswitching step and a plunger displacing step according to the followingtable:

Sub Step Sequence Step Type Description Charging (a) valve Moving themovable member into its switching charging valve position, thus closingthe discharging valve followed by opening the charging valve (b) plungerDisplacing the plunger in the distal displacing direction, thus drawingfluid via the charging valve out of a drug reservoir and into themetering cavity Dis- (c) valve Moving the movable member into itscharging switching discharging valve position, thus closing the chargingvalve followed by opening the discharging valve. (d) plunger Displacingthe plunger in the proximal displacing direction, thus forcing fluid viathe discharging valve out of the metering cavity and into the outletassembly.

The movable member is coupled for the valve switching steps and isdecoupled for the plunger displacing steps. Because the plungermaintains its position in the metering cavity along the displacementaxis for the valve switching steps, while the movable member maintainsits position for the plunger displacing steps, the valve switching stepsand the plunger displacing steps are separated from each other such thatno substantial errors result from moving the movable member. Asdescribed below in further detail, embodiments of the dosing unitsaccording to the present disclosure perform all steps of a meteringsequence and control the transition between the steps using only onedriving unit.

In some embodiments, the plunger may be positioned between the distalplunger end position and the proximal plunger end position in a uniformmanner. Therefore, a dosing unit according to these embodiments allowsthe displacing steps to be interrupted and continued without influencingthe state of the charging valve and the discharging valve; that is,without performing, fully or in part, either of the switching steps.Fluid may be drawn into the metering cavity and may be forced out of themetering cavity in many small steps, which are only limited by theresolution of the drive system. This may assist in administering verysmall drug amounts, such as required, for example, in diabetes therapyby CSII. Dimensions of a dosing unit used in CSII therapy are providedbelow.

In some embodiments, the coupling and decoupling of the movable memberis controlled, at least in part, by controlling the driving direction ofthe driving unit of the infusion device. In some embodiments, couplingand decoupling of the movable member is controlled, at least in part, bycontrolling the driving direction and controlling the starting and thestopping of the driving unit. Embodiments that include these featuresare described below in more detail.

In some embodiments, the movable member is rotatable with respect to thestationary member between its charging valve position and itsdischarging valve position, where the axis of rotation is thedisplacement axis.

In some embodiments, the stationary member and the movable member aredesigned such that the movable member is limited to rotate only betweenits charging valve position and its discharging valve position. Thecorresponding angle of rotation may, for example, be 180°, but larger orsmaller angles of rotation may be used as well. For this embodiment, themovable member is supported by a rotational bearing, which may beincluded in the stationary member, as well as also including thestationary valve apertures. Additionally, or alternatively to thestationary member, other bearings may be used for supporting the movablemember. In the axial direction, the movable member may be held in afixed position.

In some embodiments that include a rotatable movable member, the plungerincludes an outside thread and the movable member comprises an insidethread. The threads enable the plunger to be displaced along the lengthof the metering cavity in a screw-like manner. In additionalembodiments, the movable member includes an outside thread while theplunger includes an inside thread. The threads are designed for athreaded engagement without substantial play and/or backlash.

In the following, the terms “thread” and “threaded” generally refer toright-hand threads as commonly used. However, left-hand-threads mayalternatively be employed with the required modifications. The flankprofile may generally be a standard thread profile or may be especiallyoptimized for play-free engagement and force and/or torque transmission,such as an Acme thread form.

The thread pitch may be selected based on such factors as maximum volumeof the metering section, dimensions of the metering cavity and requiredmetering resolution. In the framework of an ambulatory infusion devicefor CSII, the pitch may be in the range of 0.5 mm to 2 mm.

The outside thread and the inside thread transform a rotational drivingmotion into a screw-like translation motion of the plunger along thedisplacement axis in the metering cavity. The inside thread of themetering cavity may be elongated and extend over a threaded section ofthe metering cavity in a distal direction away from the metering sectionat a length corresponding to the displacement distance or longer.

For these embodiments, the plunger includes an elongated plunger shaft,where the plunger shaft projects in a distal direction from the plugsection or the plunger. The length of the plunger shaft is determined bythe plunger displacement distance. The plunger shaft includes theoutside thread at its distal end. The length of the outside thread isshorter than the length of the inside thread, and may be as short as onewinding or less.

An engagement without substantial play and/or backlash may be achievedby biasing the threaded engagement. Biasing may be achieved by using theaxial and/or radial elasticity of the plunger shaft and/or the outsidethread of the plunger. For the purpose of biasing, the plunger shaft mayinclude or be made of one or more radially elastic legs, the legscarrying the outside thread at their distal end. Elastic deformation ofthe at least one leg creates a biasing force that is exerted by theoutside thread onto the inside thread. In some embodiments, the plungerincludes at least two radially elastic legs, with each leg having anoutside threaded section, the outside threaded sections, in combination,forming the outside thread.

In some embodiments, other means for biasing the treaded engagement inaddition or alternatively to radially elastic legs may be used. Suchbiasing means include an inherently radially elastic outside thread oraxial biasing of the threaded engagement. In some embodiments, thethreaded section of the movable member is radially elastic for biasingthe threaded engagement.

In some embodiments, the dosing unit includes a plunger coupler that isadapted to couple to the driving unit, where the plunger couplertransmits a driving torque about the displacement axis and slidinglyengages the plunger as to rotate the plunger about the displacement axiswithout substantial force transmission.

Embodiments that use the plunger coupler described above also include arotating motion of the movable member and a plunger, which displaces ina screw-like manner within the metering cavity, as described above.Where not stated differently, this embodiment is assumed in theembodiments discussed below.

In some embodiments, the plunger driver is telescopically received bythe plunger or a plunger coupler, and is in axial alignment with theplunger. In other embodiments, a drive coupler of the driving unit isdirectly coupled to the plunger without an additional plunger coupler.

As used herein, the driving direction of the driving unit for moving themovable member into the charging valve position is referred to as“charging valve direction” while the driving direction of the drivingunit for moving the movable member into the discharging valve positionis referred to as “discharging valve direction”, the charging drivingdirection and the discharging driving direction being opposite to oneanother.

In some embodiments, operating the driving unit in a charging drivingdirection results in the movable member moving into the charging valveposition, followed by displacing the plunger in the distal direction,and operating the driving unit in a discharging driving directionopposite to the charging driving direction results in the movable membermoving into the discharging valve position, followed by displacing theplunger in the proximal direction.

For a “valve before plunger” design, the movable member decouples uponadopting either of the charging valve position or the discharging valveposition. Coupling may be achieved by stopping and/or reversing thedriving direction. Embodiments of this type are in the followingreferred to as “valve before plunger” designs.

Here and in the following, the terms “reversing” and “reversible”generally refer to the driving direction in which a driving unit coupledto the dosing unit is operated.

In alternative embodiments, operating the driving unit in a chargingdriving direction results in displacing the plunger into the distalplunger end position, followed by moving the movable member in thedischarging valve direction, and operating the driving unit in adischarging driving direction opposite to the charging driving directionresults in displacing the plunger into the distal plunger end position,followed by moving the movable member in the discharging valvedirection.

Embodiments of this type are in the following referred to “plungerbefore valve” designs.

For a “plunger before valve” design, the movable member couples upon theplunger, assuming either of the proximal plunger end position or thedistal plunger end position, respectively, and decouples upon displacingthe plunger out of the proximal plunger end position or the distalplunger end position, respectively.

The relation between the single steps of a metering sequence and thedriving direction is summarized for both “valve before plunger” designsas well as “plunger before valve” designs in the following table.

Design Step Sub-Sequence Driving Direction valve (a) charging sequencecharging driving direction before (b) plunger (c) discharging sequencedischarging driving direction (d) plunger (a) charging sequencedischarging driving direction before (b) charging driving directionvalve (c) discharging sequence discharging driving direction (d)

It can be seen that for “valve before plunger” designs, both the stepsof the charging sub-sequence are performed with the driving unit beingoperated in one of the driving directions, while both steps of thedischarging sequence are performed with the driving unit being operatedin the other driving direction.

For “plunger before valve” designs, the driving direction is reversedbetween the switching step and the displacing step for both the chargingsub-sequence and the discharging sub-sequence.

Both types of design involve reversing the driving direction of thedrive unit to perform metering sequences. In contrast to metering unitsthat do not involve reversing the driving direction, dosing unitsaccording to the present disclosure may be beneficial for patientsafety, because the requirement for controlled reversing of the drivingdirection prevents the pump from continuously administering a drug incase the driving unit is permanently powered, for example because of adevice defect.

A dosing unit of the “valve before plunger design” may be designed tooperate as follows:

Selective coupling is achieved by transmitting a sticking friction forcefrom the plunger and/or a plug coupled to the plunger onto the movablemember. The sticking friction force may be caused by contact betweenadjacent components, and may, for example, be transferred from thecircumferential face of a plug section onto the circumferential face ofthe metering section, and/or from the outer thread onto the innerthread. Accordingly, the axial position of the plunger, along thedisplacement axis, is maintained such that the plunger movessynchronously with the movable member when moving the movable memberfrom the charging valve position into the discharging valve position orvice versa.

For embodiments of dosing units according to this type of design, theforce and/or torque required to move the movable member is substantiallysmaller than the force and/or torque required to displace the plunger.The force and/or torque ratio may be in the range from 1:2 to 1:10, andis further below a maximum force and/or torque that may be transmittedfrom the plug onto the movable member by sticking friction.

Selective decoupling is achieved by blocking further motion of themovable member such that the movable member maintains its position whilethe movable member adopts the charging valve position or the dischargingvalve position, and the driving unit is further operated in the chargingdriving direction or the discharging driving direction, respectively.The blocking of further motion of the movable member may be achieved byan arrangement of stops or breaks, as described below in more detail.Blocking the movable member results in changing the interface force ofthe plunger and/or plug and the movable member from sticking frictionengagement to sliding friction engagement.

Operation of an embodiment of a dosing unit according to this type ofdesign may be understood according to a metering sequence as summarizedin the following table.

Driving Direc- Cou- Step tion Description/Starting and Ending Positionpling (d) dis- Starting plunger position: any position distal nocharging from proximal plunger end position, for example, a distalplunger end position; Ending plunger position: any position proximalfrom starting plunger position, for example, a proximal plunger endposition; Movable Member: fixed in discharging valve position. (a)charging Starting movable member position: discharging yes valveposition; Ending movable member position: charging valve position. (b)charging Starting plunger position: ending plunger no position of step(d), above; Ending plunger position: any position distal from startingplunger position, for example, a charged plunger; Movable member: fixedin charging valve position. (c) dis- Starting movable member position:charging yes charging valve position; Ending movable member position:discharging valve position.

Further aspects, as well as alternative “valve before plunger” designs,are described below in greater detail.

A dosing unit of the “plunger before valve” design may be designed in asimilar way as described above. However, the force and/or torquerequired to move the movable member is substantially larger than theforce and/or torque required to displace the plunger, and is furtherbelow a maximum force and/or torque that may be transmitted onto themovable member as sticking friction force. The force and/or torquerequired for moving the movable member may be adjusted by adjusting thevalve sealing force between the movable member and the stationary memberor an additional bearing friction force of the movable member.

For embodiments of dosing units according to this type of design, themovable member is decoupled from the plunger and/or a plug coupled tothe plunger such that the movable member maintains its position so longas the plunger does not adopt either the proximal plunger end positionor the distal plunger end position. Coupling is achieved by blockingfurther displacement in the proximal direction if the plunger adopts theproximal plunger end position and by blocking further displacement inthe distal direction if the plunger adopts the distal plunger endposition. The blocking may be achieved by an arrangement of stops and/orblocks. In some embodiments, blocking is achieved by the outside threadof the plunger contacting an end of inside thread of the meteringcavity. If further displacement of the plunger is blocked, the plungermaintains its position along the displacement axis and movessynchronously with the movable member when moving the movable memberfrom the charging valve position into the discharging valve position orvice versa.

It should be noted that for embodiments of dosing units according tothis type of design, the force and/or torque required to move themovable member is, at least in part, transmitted onto the movable memberby axial contact force resulting from exerting a force and/or torqueonto the plunger that forces the plunger in a blocked displacingdirection.

For some embodiments of dosing units, such as the “valve before plunger”design described above, switching between a charging sub-sequence and adischarging sub-sequence is possible at any position of the plungerbetween the proximal plunger end position and the distal plunger endposition by reversing the driving direction. With embodiments of thisdesign, the metering cavity may be fully charged to the maximum meteringvolume whenever required. This may be beneficial, for example, if a drugbolus that exceeds the current metering volume resulting from thecurrent position of the plunger has to be administered to a patient.

For alternative embodiments, such as the “plunger before valve” designdescribed above, switching between the charging sequence and thedischarging sequence by reversing the driving direction is possible onlyif the plunger is in one of the proximal plunger end position or thedistal plunger end position. For embodiments of dosing units accordingto this type of design, a drug bolus that exceeds the current meteringvolume resulting from the current plunger position may be administeredin two or more steps, between which the metering cavity is recharged tothe maximum metering volume.

In some embodiments, the dosing unit includes an arrangement ofstationary stops and movable stops, where the movable member decouplesfrom the plunger when a movable stop engages a corresponding stationarystop, and the movable member couples to the plunger when a movable stopdisengages a corresponding stationary stop.

For some embodiments, the movable member includes two rigid movablestops made, e.g., by one or multiple cams, which may be arranged, forexample, at the outer face of the movable member or at the proximalfront or the distal front of the movable member. The rigid movable stopsare adapted to engage two corresponding stationary stops such that themovable member is limited to rotate between its charging valve positionand its discharging valve position. In alternative embodiments, themovable stops are formed by end pieces of at least one spring, thespring belonging to a wrap spring clutch, as will be described below ingreater detail.

In some embodiments, the movable member is adapted to selectively couplethe plunger by radial and/or axial contact force. Some embodimentsinvolving selective coupling by radial and/or axial contact force arethe “valve before plunger” design and the “plunger before valve” designdescribed above, and which are further described below.

In some embodiments, radial and/or axial contact force is controlledbased on the axial position of the plunger in the metering cavity and/orin based on the position of the movable member with respect to thestationary member.

One embodiment for a dosing unit with controlled axial contact force isthe “plunger before valve design” as described above, and which furtherdesigns are described below.

Controlling radial and/or axial contact force may be beneficial becauseit avoids relying only on the contact force, in particular radialcontact force as defined by design factors such as material combinationand dimensions for moving the movable member, and therefore increasesrobustness and reliability, in particular under the aspect of largescale manufacture.

In some embodiments involving controlled radial contact force, radialcontact force is controlled by controlling a radial dimension of theplunger.

In some embodiments, the radial dimension of an outside thread iscontrolled by selective radial deflection of the at least one leg.Therefore, the plunger includes a plunger shaft with at least oneplunger shaft cam, the at least one plunger shaft cam being adapted toselectively engage at least one proximal plunger coupler cam of aplunger driver if the plunger adopts the proximal plunger end position,and to selectively engage at least one distal plunger coupler cam of aplunger driver if the plunger adopts the distal plunger end position,where the engagement increases the contact force between the movablemember and the plunger.

The plunger may include an elongated plunger shaft that includesradially elastic legs with outer threads as described above. Plungershaft cams are provided at the distal end sections of the legs in radialalignment with the outer threads. The plunger coupler includes anelongated plunger coupler shaft, which may be telescopically received bythe plunger, and includes the plunger coupler cams, where the at leastone proximal plunger coupler cam is located at the proximal end of theplunger coupler shaft and the distal plunger coupler cam is located atthe distal end of the plunger coupler shaft. The plunger coupler camsmay be ramp-like in order to allow smooth engagement.

By an engagement of the at least one proximal plunger coupler cam withthe at least one plunger shaft cam, the at least one leg of the plungershaft is radially deflected towards the circumferential inside face ofthe metering cavity, thus increasing the contact force of the threadedengagement, when the plunger is in the proximal plunger end position,i.e., in its most proximal position.

By an engagement of the at least one distal plunger coupler cam with theat least one plunger shaft cam, the at least one leg of the plungershaft is radially deflected towards the circumferential inside face ofthe metering cavity, thus increasing the contact force of the threadedengagement, when the plunger is in the distal plunger end position,i.e., in its most distal position.

In some embodiments, the plunger shaft includes at least two legs, eachleg including a plunger shaft cam, and the plunger coupler shaftincludes an identical number of corresponding proximal plunger couplercams and distal plunger coupler cams.

For embodiments of dosing units according to this type of design, aswell as for embodiments that include controlled axial contact force asdescribed above, releasing the contact force after performing a valveswitching step requires considerable force and/or torque, which may beprovided by the driving unit. This force and/or torque peak may beevaluated as force and/or torque feedback.

In some embodiments, the dosing unit comprises a wrap spring clutch, thewrap spring clutch selectively decoupling the movable member when themovable member adopts either of its charging valve position or itsdischarging valve position.

A spring of the wrap spring clutch may be arranged in a distal clutchsection of the metering cavity and in axial alignment with thedisplacement axis. Alternatively, a spring of the wrap spring clutch isarranged outside the metering cavity. A spring of the wrap spring clutchmay include the movable member.

In some embodiments that include a wrap spring clutch, a spring of thewrap spring clutch selectively couples a plunger coupler and the movablemember. The spring may be wrapped around a distal plunger couplersection, the distal plunger coupler section and the spring beingdesigned such that the windings of the spring are in sticking frictionengagement with the distal plunger coupler section due to radial contactforce. The plunger coupler further includes a proximal plunger couplersection, the proximal plunger coupler section being adapted to transmita driving torque onto the plunger and to be in sliding axial engagementwith the plunger. The spring is further attached to and/or in forcetransmission engagement with the movable member.

In some embodiments involving a wrap spring clutch, one end section of aspring of the wrap spring clutch acts as movable charging stop andanother end section of a spring of the wrap spring clutch acts asmovable discharging stop, the movable charging stop being adapted toengage a stationary charging stop when the movable member adopts thecharging valve position and the movable discharging stop being adaptedto engage a stationary discharging stop when the movable member adoptsthe discharging valve position, thus decoupling the movable member.

The movable charging stop and the movable discharging stop may bestraight end sections of a coil spring which are arranged in axialalignment with the displacement axis. The end sections may project outof the metering cavity in a radial direction through a clutch aperturein the circumferential wall of the metering cavity, and the stationarystops are arranged outside the movable member. Upon either of themovable stops engaging the corresponding stationary stop, the corediameter of the spring is elastically widened, thus reducing contactforce and changing the sticking friction engagement with the plungercoupler into a sliding friction engagement and decoupling the movablemember.

Further aspects of designs of dosing units including a wrap springclutch, as well as its operation, are described below in the frameworkof one embodiment.

In some embodiments, the dosing unit includes or is adapted to couple toa movable member position detection unit and/or a plunger positiondetection unit. A movable member position detection unit may be providedand used to detect if the movable member is in either of its chargingvalve position or its discharging valve position for controlling thedriving unit of the infusion pump and/or as additional safety element.For this purpose, arrangements known in the art, such aselectro-mechanical end switches, electrical contacts or light barriers,may be used. In a similar way, a plunger position detection unit may beprovided and used to detect if the plunger is in either of the distalplunger end position or the proximal plunger end position. A plungerposition detection unit may further be adapted to determine the positionof the plunger between the charging plunger valve position and itsdischarging valve position, and may be provided for the same purposes asa movable member position detection unit. For this purpose, a plungerposition detection unit may comprise sensors known in the art, such asvariable resistors, CCD sensors or position detection sensors (PDSs) anda corresponding processing circuit.

In order to detect the occurrence of valve leakages, the dosing unit mayinclude or is operatively coupled to at least one valve leakagedetector. Valve leakage detectors may be utilized by providingelectrical circuits that are generally open and are closed by aconductive drug, such as insulin, in case of a leakage. In someembodiments, both a charging valve leakage detector and a dischargingvalve leakage detector are provided.

In a further aspect, the present disclosure is directed towards afluidic assembly, including:

a) a dosing unit as described above; and

b) a drug reservoir, the drug reservoir being in fluidic connection withthe inlet valve of the dosing unit.

The dosing unit and the drug reservoir may be designed as integral unit.In some embodiments, the dosing unit and the drug reservoir are designedto be a disposable item that is discarded after emptying the drugreservoir. In alternative embodiments, the drug reservoir is adapted tobe refilled, e.g., via a septum.

The drug reservoir may be of any design known in the art for this typeof application and may, for example be realized as a cylindricalcartridge, a bag, a pouch, or the like. In some embodiments, the drugreservoir is a bag that may additionally be spring-loaded.

In a further aspect, the present disclosure is directed towards anambulatory infusion device. An ambulatory infusion device according tothe present disclosure includes:

a) a reversible driving unit;

b) a drug reservoir, the drug reservoir being adapted to comprise theliquid drug;

c) a dosing unit as described above, the charging valve of the dosingunit being in fluidic connection with the drug reservoir, the dosingunit being coupled to the driving unit;

d) an outlet assembly in fluidic connection with the discharging valveof the dosing unit; and

e) a controller unit adapted to control the driving unit for druginfusion over the extended time period.

The reversible driving unit may include a rotary drive such as a DCmotor, a brushless DC motor or a stepper motor, and may further includea reduction gear. The reversible drive may further include drive sensorssuch as optical encoders, hall encoders and/or a revolution speedsensor. The reversible driving unit may include a drive coupler, thedrive coupler being adapted to transmit a driving force and/or torque tothe dosing unit.

The term “outlet assembly” refers to any element or a combination ofelements downstream from the dosing unit and being adapted for fluidicconnection with the outlet valve of the dosing unit. In particular, theoutlet assembly may include a subcutaneous infusion cannula and/or afluidic element to be coupled to an infusion cannula and a dosing unitaccording to the present disclosure, such as an infusion line, aninfusion line connector, a check valve, a pressure measurement unit, orthe like.

The controller unit may include components known in the art such asmicrocontrollers, ASICS, volatile and/or non-volatile memory components,and the like. The controller unit may be coupled to and/or include auser interface, such as push buttons, a display, audio and/or tactileindicators, and the like. The controller unit may include or isoperatively coupled to at least one communication interface such as anIR interface and/or an RF interface.

The ambulatory infusion device may further include at least one powersupply such as a rechargeable and/or a non-rechargeable battery.

The ambulatory infusion device may include a housing, which may be asingle housing enclosing all components and/or may be made of more thanone housing adapted to physically and/or operatively couple to eachother. For example, the housing may be made of a first housing enclosingdurable components such as the controller unit, that drive a userinterface, and the like, while disposable components, for example thedosing unit and the drug reservoir, are enclosed by a second housing.For embodiments according to this type of design, the power supply mayincluded in either of the first housing or the second housing.

In some embodiments, the dosing unit is, at least in part, integral withthe drug reservoir and/or the output unit.

The ambulatory infusion device may, at least in part, include sensorsand/or detection units such as movable member position detection unitsand/or a plunger position detection unit as described above, a driveforce and/or torque sensor, a fluidic pressure sensor and the like. Aforce and/or torque sensor may be employed for detecting the plungertraveling to either of the distal plunger end position and the proximalplunger end position, as well as the movable member traveling to eitherof its charging valve position or its discharging valve position,because the occurrence of these situations is associated with a jumpand/or peak in the driving force. Additionally or alternatively to forceand/or torque measurement, the current supplied to a drive motor may beevaluated as a measure of the driving force and/or torque.

The dosing unit and the outlet assembly may be disposable units and mayhave a typical lifetime of a few days, after which they are discardedand replaced. The other components of the device are durable and have alonger lifetime of, for example, some years, or a generally open andunlimited lifetime.

An ambulatory infusion device according to the present disclosure may bedesigned for the therapy of diabetes mellitus by CSII therapy. For thisapplication, the drug reservoir may be adapted to store the insulinamount required, for example, for, one week of therapy, which may be inthe range of 200 to 500 IU (International Units), corresponding to 2 to5 ml of insulin in the concentration U100. However, larger or smallerdrug volumes and/or drug concentrations may be used as well.

Further capabilities and aspects of an ambulatory infusion device fordiabetes therapy, while not explicitly mentioned, may be obvious forsuch devices for a person ordinary skilled in the art. Besides diabetestherapy, ambulatory infusion devices according to the present inventionmay be used for therapies such as cancer therapy or pain therapy withoutsubstantial modifications.

According to a still further aspect of the present disclosure, thedisclosure is directed towards a method for operating a metering unitfor an ambulatory infusion device, the method including the steps of:

a) providing a dosing unit and a driving unit;

b) coupling a plunger of the dosing unit, the plunger being located, atleast in part, in a metering cavity of a movable member of the meteringunit and being adapted for displacement in the metering cavity along adisplacement axis;

c) coupling the movable member of the dosing unit to the driving unitwith the plunger being further coupled to the driving unit;

d) moving the movable member into a charging valve position with aposition of the plunger relative to the movable member along thedisplacement axis being maintained;

e) decoupling the movable member from the driving unit (505) with theplunger being further coupled to the driving unit;

f) displacing the plunger along the displacement axis in a distaldirection with the position of the movable member being maintained, thuscharging the metering cavity;

g) coupling the movable member of the dosing unit with the driving unit,with the plunger being further coupled to the driving unit;

h) moving the movable member into a discharging valve position, with theposition of the plunger relative to the movable member along thedisplacement axis being maintained;

i) decoupling the movable member from the driving unit with the plungerbeing further coupled to the driving unit; and

k) displacing the plunger along the displacement axis in a proximaldirection with the position of the movable member being maintained, thusdischarging the metering cavity.

In some embodiments, the steps (d) to (k) of the method are preformed ina cyclic manner and after performing the steps (a) to (c). Furtheraspects of the method, as well as embodiments for carrying out themethod, are described above in the framework of a dosing unit accordingto the present disclosure.

In some embodiments, the method includes performing the steps (d) and(f) by operating the driving unit in a charging driving direction andperforming the steps (h) and (j) by operating the driving unit in adischarging driving direction, the charging driving direction beingopposite to the discharging driving direction. Carrying out the methodaccording to this embodiment corresponds to a “valve before plunger”design of the dosing unit, as described above.

In alternative embodiments, the method includes performing the steps (f)and (h) by operating the driving unit in a charging driving directionand performing the steps (j) and (d) by operating the driving unit in adischarging driving direction, the charging driving direction beingopposite to the discharging driving direction. Carrying out the methodaccording to this embodiment corresponds to a “plunger before valve”design of the dosing unit, as described above.

In the following, exemplary dosing units in accordance with the presentinventions which may be used in ambulatory infusion devices according tothe present disclosure, corresponding methods for controlling operationof a dosing unit according to the present disclosure and an embodimentof the ambulatory infusion device according to the present disclosureare described with reference to the figures.

FIG. 1 depicts a dosing unit 1 according to one embodiment of thedisclosure in a local section isometric view, with the circumferentialwall 36 being partly cut away such that the elements located inside themetering cavity 31 are more clearly visible.

The dosing unit 1 includes a movable member 30 and a stationary member20. The movable member 30 substantially has the shape of a hollowcylinder having a closed proximal front 34 and an open distal front 49.The movable member 30 further has a circumferential wall 36 and aproximal front wall 32 such that it forms a hollow cylinder, the innervolume of which forms the metering cavity 31. The displacement axis A isthe axis of symmetry of the movable member (shown in FIG. 1 shiftedparallel to for purposes of clarity).

The movable member 30 is rotationally supported by the stationary member20. A bearing is formed, in combination, by the circumferential outerface 40 of the circumferential wall 36, the proximal front 34 and abearing surface (not visible) of the stationary member 20. Thedimensions and tolerances of the movable member 30 and the stationarymember 20 are such that the contacting area of the circumferential outerface 40 and the bearing surface of the stationary member 20, incombination, form a fluid-tight seal. The movable member 30 and/or thestationary member 20 may have some radial elasticity in order to ensuresealing. Alternatively, both the movable member 30 and the stationarymember 20 are made from generally “hard” materials, e.g. asinjection-molded plastic components, where one of the movable member 30or the stationary member 20 is harder than the other for optimalsealing.

A movable cam 80 projects from the proximal front 34 in proximaldirection III, the movable cam 80 having a movable charging stop 82 anda movable discharging stop 84 formed by faces of the movable cam 80. Themovable charging stop 82 engages a stationary charging stop 22 when themovable member is in its charging valve position and the movabledischarging stop 84 engages a stationary discharging stop 24 when themovable member is in its discharging valve position. The stationarystops 22, 24 are formed by faces of the stationary member 20. Incombination, the stops 22, 24, 82, 84 limit the rotation of the movablemember 30 between the charging valve position and the discharging valveposition.

A movable valve aperture 70 passes through the circumferential wall 36of the movable member 30 in proximity to the proximal front 34.

A charging connector 72 creates a fluid connection between thestationary member 20 and a drug reservoir (not shown) and a dischargingconnector 74 creates a fluid connection between the stationary member 20and an outlet assembly (not shown). The charging connector 72 and thedischarging connector 74 are inserted into a corresponding chargingvalve bore (not visible) and discharging valve bore (not visible) of thestationary member 20, the valve bores forming stationary valveapertures. The position of the bores in the stationary member 20 aresuch that the movable valve aperture 70 is in alignment with thecorresponding charging valve bore when the movable member 10 is in itscharging valve position, and the movable valve aperture 70 is inalignment with the discharging valve bore when the movable member 30 isin its discharging valve position. In order to reduce the requirementsfor tight manufacturing tolerances, the dimensions of the stationaryvalve apertures, that is, the diameters of the valve bores wherecontacting the circumferential outer face 40 of the movable member 30,may be somewhat larger than the diameter of the movable valve aperture70. Further, the valve bores may be chamfered in locations proximate tothe movable member 30.

A plunger 50 is located inside the metering cavity 31. The plunger 50includes an elongated plunger shaft 60 (shown transparent in FIG. 1).The plunger shaft 60 adjoins a plug 52 and projects from the distal plugfront 58 in distal direction IV. The plunger shaft 60 includes anoutside thread 62 near its distal end. The plug 52 and the plunger shaft60 may be integrally formed by injection molding, but may also beassembled from a number of components. The outside thread 62 of theplunger shaft 60 is in threaded and substantially play-free engagementwith a corresponding inside thread 42 of a distal section of themetering cavity 31. The length that the inside thread 42 extends alongthe metering cavity 31 is determined by the required plungerdisplacement distance. The section of the metering cavity 31 located inthe proximal direction III from the inside thread 42 is the meteringsection 39.

In the distal plunger end position, the distal plug front 58 adjoins thedistal end 46 of the metering section 39. While not shown, a furtherstop may be provided at the distal front 49 which engages the distalshaft end 59 in the distal plunger end position as to limit the travelof the plunger 50 in the distal direction IV. In the proximal plungerend position, the proximal plug front 54 substantially adjoins the innerface (not visible) of the proximal front wall 32 of the movable member30.

Axial translation of the plunger 50 is accordingly limited between thedistal plunger end position and the proximal plunger end position withthe plug 52 being located in the metering section 39 of the meteringcavity 31. The proximal plug front 54, the circumferential face 38 ofthe metering section 39 and the inner surface (not visible) of theproximal front wall 32, in combination, form the variable meteringvolume.

The plunger shaft 60 comprises an elongated coupler hole 65 of squarecross section, which is adapted to telescopically receive a drivecoupler 90 of a reversible driving unit (further components of drivingunit not shown), such that the drive coupler 90 transmits a drivingtorque onto the plunger 50 but is in axial sliding engagement with theplunger 50.

Coupling of the movable member 30 is performed by transmitting asticking friction force from the circumferential face 53 of the plug 52onto the circumferential face 38 of the metering section and from theoutside thread 62 onto the inside thread 42.

A dosing unit 1 according to this embodiment may be designed as eitherof “valve before plunger” or “plunger before valve” design. If thetorque required for rotating the movable member between the chargingvalve position and the discharging valve position is below the torquerequired for displacing the plunger, the dosing unit 1 acts is a “valvebefore plunger” design; otherwise it is a “plunger before valve” design.

The description as given above is a “valve before plunger” design. For a“plunger before valve design”, the role of the inlet valve and theoutlet valve, and thus of the charging tube and the discharging tube,are reversed. That is, for a “plunger before valve design” elementnumber 74 refers to the inlet tube and element number 72 to the outlettube.

For a “valve before plunger” design, changing between a chargingsub-sequence and a discharging sub-sequence may be performed byreversing the driving direction for any plunger position.

For a “plunger before valve” design, changing between a chargingsequence and a discharging sequence is possible only if the plunger isin either of its end positions, that is, in the distal plunger endposition or the proximal plunger end position, respectively.

For both designs, it is assumed that the torque required for rotatingthe movable member 30 within the stationary member 20 does not exceed amaximum force that may be transmitted via sticking friction.

Several variations of this embodiment may be obvious for a personskilled in the art. For example, the cross-section of the cross sectionof the drive coupler 90 and the coupler hole 65 may be different fromsquare, the movable valve aperture 70 may be provided at the proximalfront wall 32, the arrangement of stops may be different, and the like.

FIG. 2 shows another embodiment of a dosing unit 2 according to thepresent disclosure in a view similar to FIG. 1. The aspects of thisembodiment that differ from the embodiment shown in FIG. 1 and describedabove are primarily discussed below. It should be noted that in contrastto FIG. 1, FIG. 2 depicts the dosing unit from the distal side, that is,from the drive side.

With respect to the bearing, the movable member 130 and the valveapertures, the design of the stationary member 120 is analogous to thestationary member 20 described above in regard to FIG. 1. However, anarrangement of stationary stops is not provided at the stationary member120 depicted in FIG. 2.

While the inside thread 142 and the metering section 139 of the meteringcavity 131 depicted in FIG. 2 are designed as described above in regardto FIG. 1, the movable member 130 further comprises a clutch section 200located in a distal direction IV from the inside thread 142. In theclutch section 200, the circumferential wall 136 of the movable member130 comprises an elongated clutch aperture 205 that extends in axialdirection, the distal clutch aperture end 207 adjoining the distal front149 of the metering cavity 131 and thus the distal front of thecircumferential wall 136.

The plunger 150 comprises a distal outer thread 162, an elongatedplunger shaft 160, and a proximal plug section 152.

A plunger coupler 210 is provided, the plunger coupler 210 having acircular distal plunger coupler section 212 in the area of the clutchaperture 205 and a proximal plunger coupler section 214 is received by acoupler hole of square cross section (not visible in FIG. 2) of theplunger 150 of square or generally non-linear cross section. Theproximal plunger coupler section 214 fulfills the same function as thedrive coupler 90 of the exemplary embodiment as described above inregard to FIG. 1. The distal plunger coupler section 212 is adapted tocouple to a drive coupler (not shown) of a reversible driving unit. Theplunger coupler 210 is adapted to perform a rotary motion but to stay inplace in an axial direction relative to the movable member 130.

A coil spring 220 is wrapped around the distal plunger coupler section212, where the length of the coil spring 220 and the axial position ofthe coil spring 220 on the distal plunger coupler section 212 are suchthat the distance between the proximal spring end 282 and the distalspring end 284 is less than the depth of the clutch aperture 205. Theinternal diameter of the coil spring 220 is such that the windings ofthe coil spring 220 are in frictional sticking contact with the distalplunger coupler section 212, i.e., prior to installation, the internaldiameter of the coil spring 220 is somewhat smaller than the diameter ofthe distal plunger coupler section 212. At approximately the middle ofits length, the coil spring 220 is further fixed to the innercircumferential face of the movable member 130 (fixture not visible),such that a force and/or torque can be transmitted from the plungercoupler 210 onto the movable member 130 via the coil spring 220,resulting in the movable member 130 being rotationally coupled to theplunger coupler 210. The coil spring 220 may have three to ten windings,but may also have less windings and even have less than one completewinding.

The proximal spring end 282 and the distal spring end 284 radiallyproject out of the clutch aperture 205. The proximal spring end 282 actsas a movable charging stop and the distal spring end 284 acts as amovable discharging stop. The proximal spring end 282, acting as themovable charging stop, may engage a stationary charging stop 222 and thedistal spring end 284, acting as the movable discharging stop, mayengage a stationary discharging stop 224.

If either of the movable stops 282, 284 engages the correspondingstationary charging or discharging stop 222, 224, providing furtherdriving torque to the plunger coupler 210 results in the windings of thecoil spring 220 being widened (i.e., at least partially unwound),resulting in the coil spring 220 and the distal plunger coupler section212 changing from sticking friction engagement to sliding frictionengagement, thus rotationally decoupling the movable member 130 from theplunger coupler 210.

For this embodiment, the movable member 130 is in the decoupled state ifthe movable member 130 is in either of the charging valve position orthe discharging valve position and in the coupled state otherwise.Reversing the driving direction of the plunger coupler 210 results inthe engagement of a movable stop (i.e., the proximal and distal springends 282, 284) and a corresponding stationary charging or dischargingstop 222, 224, to be released, thus rotationally coupling the movablemember 130 to the plunger coupler 210.

As can been seen from the description, this dosing unit 2 depicted inFIG. 2 acts as “valve before plunger” design and allows for changingbetween a charging sub-sequence and a discharging sub-sequence at anyplunger position by reversing the driving direction of the plungercoupler 210. However, unlike a “valve before plunger design” accordingto FIG. 1, the embodiment depicted in FIG. 2 does not rely on plungerfriction and/or thread friction for moving the movable member.

Several variations of this embodiment may be obvious for a personskilled in the art. For example, instead of one coil spring 220 that isfixed to the movable member 130 near the middle of its length, twoseparate coil springs may be used. In alternative embodiments employingone coil spring 220, the coil spring 220 is not fixed to the movablemember 130. Instead, engagement of the movable charging stop, i.e., theproximal spring end 282, or the movable discharging stop, i.e., thedistal spring end 284, with the edges of the clutch aperture 205 may beused for force and/or torque transmission from the plunger coupler 210to the movable member 130. Furthermore, the distal plunger couplersection 212 may not be circular, but instead include a cross sectionhaving a different shape that allows transmitting a sticking frictionforce onto the coil spring 220, such as a hexagon cross section.

FIG. 3 a and FIG. 3 b show a dosing unit 3 according to a still furtherexemplary embodiment of the present invention. FIG. 3 a shows themovable member and the plunger in a perspective partial section view,while FIG. 3 b shows an exploded view of the dosing unit 3 depicted inFIG. 3 a. As discussed below, reference is made to both FIG. 3 a andFIG. 3 b. The stationary member of this embodiment is not shown and maybe designed in an analogue way to the previously described embodiments.

The movable member 330 including the movable valve aperture, here theplunger coupler 370, and the metering cavity 331 may be designed in ananalogue way to the previously described embodiments depicted in FIGS. 1and 2. The plunger 350 includes a plug 352 and an elongated plungershaft 360. The plunger shaft 360 and the plug 352 are coupled to oneanother by a plug coupler 353 located at the proximal end of the plungershaft 360 and a corresponding aperture (not visible) in the distal frontof the plug 352. Alternatively, the plug 352 may be integral with theplunger shaft 360.

The plunger coupler 370 includes a coupler body 371, the coupler body371 abuts the movable member 330 along the distal end of the movablemember 330 and includes a coupler aperture 372 of non-circularcross-section. The coupler aperture 372 is adapted to engage a drivecoupler (not shown) of a driving unit (not shown) of the infusiondevice.

The plunger coupler 370 includes an elongated plunger coupler shaft 373that extends in a proximal direction from the coupler body 371, wherethe length of the plunger coupler shaft being 373 is defined by therequired plunger displacement distance.

The plunger coupler shaft 373 has a cross-like cross section with fourelongated protrusions. Two of the opposing protrusions are force and/ortorque transmission protrusions. FIG. 3 a shows one of the force and/ortorque transmission protrusions 375; the second one is hidden in thisview. The other two opposing protrusions are cam protrusions 377 a, 377b, the function of which is described below. The cam protrusions 377 a,377 b include ramp-like proximal plunger coupler cams 378 a, 378 b anddistal plunger coupler cams 379 a, 379 b located at the proximal anddistal end of the plunger coupler shaft 373, respectively.

The elongated plunger shaft 360 includes two elongated and radiallyelastic legs 362 a, 362 b. The legs 362 a, 362 b have distal outsidethreads 363 a, 363 b that are in threaded engagement with an insidethread 342 of the movable member 330. Between the legs 362 a, 362 b,force and/or torque transmission slits 380 are provided. FIG. 3 a andFIG. 3 b depict one of the force and/or torque transmission slits 380;the second force and/or torque transmission slit is hidden in this view.The plunger shaft 360 is designed such that the legs 362 a, 362 areslightly inwardly deflected by the threaded engagement, such that aradial biasing force is exerted by the outside thread 363 a, 363 b ontothe inside thread 342, resulting in a play-free threaded engagement.Because the length of the outside thread 363 a, 363 b is only onewinding, the biasing force is substantially constant over the length ofthe threaded engagement. The force and/or torque transmission slits 380receive and slidingly engage the force and/or torque transmissionprotrusions 375, such that the force and/or torque transmissionprotrusions 375 are telescopically received by the plunger shaft 360.

The plunger shaft 360 comprises two cam receiving slits. FIG. 3 a showsone of the cam receiving slits 382, the second one is hidden in thisview. The cam receiving slits 382 slidingly receive the cam protrusions377 a, 377 b. The cam receiving slits 382 do not extend over the fulllength of the legs 362 a, 362 b. In particular, the distal ends 383 ofthe cam receiving slits 382 are located in a proximal direction III fromthe outside threads 363 a, 363 b.

If the plunger 350 is located in neither of the distal plunger endposition, nor the proximal plunger end position, the proximal plungercoupler cams 378 a, 378 b are slidingly received by the cam receivingslits 382 without a radial force being exerted on the proximal plungercoupler cams 378 a, 378 b. Therefore, the plunger 350 may be displacedwith the movable member 330 being decoupled from the plunger coupler370.

If the plunger 350 adopts the distal plunger end position, the distalplunger coupler cams 379 a, 379 b engage the plunger cams 366 a, 366 b,the plunger cams 366 a, 366 b being made of the distal portions of thelegs 362 a, 362 b in radial alignment with the outside threads 363 a,363 b. In an analogue way, if the plunger 350 adopts the proximalplunger end position, the proximal plunger coupler cams 378 a, 378 bengage the plunger cams 366 a, 366 b. Due to the cam engagement, thelegs 362 a, 362 b are deflected outwards. In doing this, the contactforce between the outside threads 363 a, 363 b and the inside thread 342is increased, such that the movable member 330 is coupled to the plungercoupler 370.

Even though not shown, an arrangement of movable stops at the movablemember 330 and of stationary stops is provided such that the movablemember 330 is limited to rotate between its charging valve position andits discharging valve position, as described above in regard to FIGS. 1and 2.

Because the movable member 330 is coupled to the plunger coupler 370only if the plunger 350 is positioned in either of the distal plungerend position or in the proximal plunger end position, switching betweena charging sub-sequence and a discharging sub-sequence may be performedonly in this end positions of the plunger 350.

A dosing unit 3 according to this embodiment is a “valve before plunger”design. Switching from a valve switching step to a plunger displacingstep may involve a considerable amount of force, because the contactforce between the outside thread 363 a, 363 b, and the inside thread 342has to be first released. For a “valve before plunger”, design, themovable member 330 is further forced in the charging valve direction ifthe movable member 330 has previously been rotated into the chargingvalve position and is forced in the discharging valve direction if themovable member has previously been rotated into the discharging valveposition. Further rotation of the movable member, however, is blocked bythe stop arrangement (not shown).

FIG. 4 shows a schematic structural view of an ambulatory infusiondevice according to the present disclosure. The dosing unit 1, 2, 3 ofthe infusion device may be any dosing unit according to the presentdisclosure as described above. The dosing unit 1, 2, 3 is coupled to adriving unit 505, which includes a rotary electric drive, for example, aDC motor, a brushless DC motor or a stepper motor, and further includesa drive coupler that transmits a driving torque onto the dosing unit 1,2, 3 as described above. The driving unit 505 may further includeintermediate drive components such as a reduction gear.

The driving unit 505 receives it electrical power and control signalsfrom the controller unit 500. The driving unit 505 may further includesensor elements such as a rotational encoder for feeding one or multiplefeedback signals into the controller unit 500. The driving unit 505 mayinclude a torque and/or a force sensor for measuring the torquetransmitted into the dosing unit 1, 2, 3. For this purpose, the drivingunit 505 may, fully or in part, be floating relative to the dosing unit1, 2, 3, as known in the art. The controller unit 500 may further beadapted to measure the drive current as a measure for the torquetransmitted into the dosing unit 1, 2, 3.

The dosing unit 1, 2, 3, is in fluidic connection with a drug reservoir510, for example, a spring-loaded bag, and an output assembly 515 thatincludes a subcutaneous cannula.

A movable member position detector 525 is coupled to or is includedwithin the dosing unit 1, 2, 3, and includes electrical contacts and/orlight barriers that detect if the movable member of the dosing unit 1,2, 3 is in the charging valve position or the discharging valveposition.

The infusion device further includes an optional administrationsupervising unit 520, which is operatively coupled to the outputassembly 515 and provides supervising information to the controller unit500. The administration supervising unit 520 may include a fluidicpressure measurement unit as known in the art for measuring andmonitoring the fluidic outlet pressure. By monitoring the fluidic outletpressure, a number of potentially hazardous situations, for exampleocclusions, may be detected, as known in the art.

Further typical elements of ambulatory infusion devices such as powersupplies, user interface data interfaces, and the like are not shown inFIG. 4, but may be present in the ambulatory infusion devices.

What is claimed is:
 1. A method for operating a metering unit for anambulatory infusion device, comprising: a) providing a dosing unit and adriving unit; b) coupling a plunger of the dosing unit, the plungerbeing located, at least in part, in a metering cavity of a movablemember of the metering unit and being adapted for displacement in themetering cavity along a displacement axis; c) coupling the movablemember of the dosing unit to the driving unit with the plunger beingfurther coupled to the driving unit; d) moving the movable member into acharging valve position with a position of the plunger relative to themovable member along the displacement axis being maintained; e)decoupling the movable member from the driving unit with the plungerbeing further coupled to the driving unit; f) displacing the plungeralong the displacement axis in a distal direction with a position of themovable member being maintained, thus charging the metering cavity; g)coupling the movable member of the dosing unit with the driving unit,with the plunger being further coupled to the driving unit; h) movingthe movable member into a discharging valve position, with the positionof the plunger relative to the movable member along the displacementaxis being maintained; i) decoupling the movable member from the drivingunit with the plunger being further coupled to the driving unit; and k)displacing the plunger along the displacement axis in a proximaldirection with the position of the movable member being maintained, thusdischarging the metering cavity.
 2. The method of claim 1, wherein steps(d) and (f) are performed by operating the driving unit in a chargingdriving direction and steps (h) and (k) are performed by operating thedriving unit in a discharging driving direction, the charging drivingdirection being opposite to the discharging driving direction.
 3. Themethod of claim 1, wherein steps (f) and (h) are performed by operatingthe driving unit in a charging driving direction and steps (k) and (d)are performed by operating the driving unit in a discharging drivingdirection, the charging driving direction being opposite to thedischarging driving direction.
 4. A method for operating a metering unitfor an ambulatory infusion device having a driving unit, said methodcomprising: providing a dosing unit which comprises a stationary memberand a movable member with the driving unit, the movable member and thestationary member, in combination, making a charging valve and adischarging valve, the charging valve is configured to be in fluidcommunication with a drug reservoir of the infusion device and thedischarging valve is configured to be in fluid communication with anoutlet assembly of the infusion device, a plunger, located, at least inpart, in a metering cavity of the movable member and is configured fordisplacement in the metering cavity along a displacement axis between adistal plunger end position and a proximal plunger end position, thedisplacement axis being a pivoting axis of the movable member, theplunger being in a threaded engagement with the movable member, whereinthe plunger is configured to couple continuously to the driving unit andthe movable member is configured to selectively couple to the drivingunit; operating the driving unit with the movable member being coupledwith the driving unit, in which the movable member moves with theplunger to maintain a position along the displacement axis and in whichthe movable member moves between a charging valve position, in which thecharging valve is open and the discharging valve is closed, and adischarging valve position, in which the discharging valve is open andthe charging valve is closed; and operating the driving unit with themovable member being decoupled from the driving unit, in which theplunger is displaced while a position of the movable member ismaintained.
 5. The method of claim 4, further comprises providing theplunger with an outside thread and the movable member with an insidethread.
 6. The method of claim 5, further comprises designing theoutside thread and inside thread for a threaded engagement withoutsubstantial play or backlash.
 7. The method of claim 6, furthercomprises providing the threaded engagement with an acme thread profile.8. The method of claim 6, further comprises providing the threadedengagement with a biasing.
 9. The method of claim 8, further comprisesachieving the biasing by at least one of radial elasticity and axialelasticity.
 10. The method of claim 5, further comprises providing theplunger with one or more radially elastic legs, the legs carrying theoutside thread at a distal end.
 11. The method of claim 7, furthercomprises inwardly deflecting the legs by the threaded engagement. 12.The method of claim 4, further comprises providing a threaded section ofthe movable member that is radially elastic.
 13. The method of claim 4,further comprises coupling and decoupling the movable member, at leastin part, by controlling the driving direction of the driving unit. 14.The method of claim 4, further comprises coupling and decoupling themovable member, at least in part, by controlling the driving direction,the starting and the stopping of the driving unit.